The exercise can bring about changes in the body physiology of a person engaging in the exercise. For this reason, the moderate exercise is often beneficial to the health of an exerciser. If the exercise is done excessively, the exercise becomes in itself hazardous to the health of the exerciser. The conventional game rackets are not provided with a device for monitoring the body condition of an exerciser. As a result, the exerciser is often unaware of the need to adjust the pace of exercise to minimize the risk of the danger resulting from the excessive exercise.